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October 2005

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Subject:
From:
Brian Ellis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Brian Ellis <[log in to unmask]>
Date:
Wed, 26 Oct 2005 18:57:59 +0300
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I could write for hours on this subject but the upshot is that the
figures for any given instrument are meaningless, unless you correlate
them to a standard method. As the standard method developed by the US
Navy had 28 variables that they did not take into account, and later
research by the European Space Agency showed that there was not even any
correlation between different flux types, different cleaning methods and
instruments, you can therefore choose whatever figure you like within
reason and nobody can prove you wrong.

In practice, you should determine the degree of cleanliness that suits
your application, as shown by ECM tests, measure, say, 20 circuits and
calculate the mean and the standard deviation, and you call that your
standard figure for that particular piece of hardware, process and
measuring method. If subsequent test fall within the same mean and SD,
or better, then you're OK as a rapid process test method.

Brian

Macko, Joe @ IEC wrote:
> Fellow techs,
>
>
>
> Good morning.
>
> We have an Omegameter 600SMD that is used to check boards for ionic
> contaminates.  The ionic residue limit within J-STD-001C, para. 8.3.6 is 10
> ug/sq. NaCl.  Some personnel believe that this number should be adjusted
> based on the actual instrument used (e.g., an Omegameter).  Would someone be
> so kind as to comment on this subject and what the correct limit is for an
> Omegameter type of instrument.
>
>
>
> Thanks
>
> joe
>
>
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